Standard tires with tubes have certain advantages. For example, tires with tubes are easier to repair as all that is required is the replacement of a punctured tube; may have the ability to maintain pressure for long periods and usually do not require special adaptation of the rim for sealing. However, utilizing tires with tubes has a number of disadvantages as well. One disadvantage is that such tires may suffer from “pinch flats” in which the tube becomes momentarily pinched between the tire casing and the rim, tearing the tube. This problem is particularly acute for mountain bikes which tend to run tires at lower pressure and over rougher terrain. Another disadvantage is their weight. Tubeless bicycle tires do not suffer pinch flats and can be lighter because of the absence of the tube itself, however, the tubeless arrangement requires a sealed rim, a bead to rim seal and an air impermeable tire. Thus, the configuration of tubeless tires has proved problematic in certain applications.
One example of such an application is when a tubeless tire is used on a bicycle that takes wider tires. This type of bicycle is commonly referred to as a “fat bike”. The tire size for these bikes is normally three to five inches wide. Correspondingly, the wheel rims (or just “rims”) used for this size tire tend to be between 50 mm to 100 mm wide (and in many cases between 65 mm and 85 mm), and the diameter is mostly the 26 inch designation but there are also 29 inch fat bikes and in the future the expectation is that there will be even more sizes such as 27.5 inch.
In a conventional tubeless tire setup for bicycles, there is a center channel in the rim that the tire beads rest in an uninflated state. During inflation of the tire when a sufficient pressure is reached within the tire bead travels (or “pops”) onto a shelf formed in the rim thereby sealing the system, holding the tire in place and allowing it to retain a desired pressure. These conventional designs are, however, inadequate for tires of larger width or in certain cases when trying to inflate the tire with a manual air pump. In the main, this is the case because as the width of the rim and the tire increases, the area between the beads of the tire as it rests on the center channel commensurately increases.
Having a center channel that holds the beads, but that is also sufficiently tight to allow a sufficient pressure to be established such that the tubeless tire “pops” onto the rim ledges is difficult In part, this is because there is a significant variation in the actual diameter of tires from different manufacturers. For example, a 26 inch tire from one manufacturer may be several millimeters larger than a 26 inch tire from another manufacturer. Moreover, there can be significant diameter differences within a single tire due to manufacturing tolerances (e.g., because the bead is warped). Therefore it can be difficult to produce a tubeless rim that works reliably.
Additionally, such a center channel may be problematic because if there is a deep well in the center of the rim it is difficult to get the beads to “behave” properly. Beads may flex or otherwise move in such a manner that creates a gap between at least one of the beads and the rim so that air escapes and a threshold pressure within the tire that would allow the tire to inflate in a “tubeless” manner (e.g., to get the beads to “pop” onto a retaining shelf) cannot be established. Such gaps are particularly likely to occur when the beads pop over a sharp transition to a retaining shelf.
To attempt to address some of these problems, certain tubeless rims have been designed for user with a particular bead size and shape. Rims of this type are, however, incompatible with any other type of tubeless tire that does adhere to such a bead size and shape.
What is desired then, is a bicycle wheel rim shaped to allow easier inflation of tires when used in a tubeless configuration and that may also be used with a wide variety of tires.